A toothed belt may be used as the transmission; however, the transmission may also include gear wheels. Usually, the transmission backlash increases constantly as a result of wear when the arrangement (production machine) is operated. If the transmission backlash becomes excessive, the operation of the machine is impaired. In the prior art the transmission backlash is monitored by the provision of purpose-made sensors. In this case, in addition to the transducer on the drive element, a second transducer (e.g. shaft encoder) is provided which determines the angular position or the position of the load downstream of the transmission. The transmission backlash is then measured directly by subtraction between the two transducers. As a rule, a second transducer is expensive.
In most cases the transmission backlash is monitored by manual checking at regular test intervals using measuring instruments. In the case of toothed belts the belt tension is measured, for example, acoustically. If the tension becomes too low and the transmission backlash therefore too large, the toothed belt is exchanged. The use of additional sensors is complex and costly. In comparison to manual monitoring of the transmission backlash, it must be ensured, in particular, firstly that excessive transmission backlash is detected reliably, and secondly that maintenance does not have to take place too early. The objective is therefore to find an optimum time for maintenance, and preferably for exchanging transmission parts.
EP 1 489 401 A1 describes a method for determining the amount of wear in a drive arrangement comprising, for example, a gear rack and a pinion. A base torque and a harmonic thereof are applied to the arrangement and a response signal, in particular the angular velocity or angular offset as a function of time, is measured by a transducer (sensor) present in the arrangement in any case. The response signal is analyzed, for example using discrete fast Fourier transformation. The response signal can be compared to a corresponding response signal which was obtained under ideal running conditions of the arrangement.
The selected harmonic of the torque is selected explicitly such that the frequency is lower than 90% of the lowest natural frequency in the arrangement. An optimum evaluation result is claimed to be obtained thereby.